Wednesday, January 02, 2019 1:00 am

Space exploration reaches new limit

Washington Post

As Earthlings marked the start of a new year, one of the most distant spacecraft successfully explored the farthest – 4 billion miles from Earth – and most primitive objects that humans have ever seen.

NASA received confirmation Tuesday that its New Horizons probe survived its 12:33 a.m. eastern encounter with Ultima Thule, a rocky relic from the solar system's infancy whose name means “beyond the borders of the known world.”

The midnight rendezvous occurred in the Kuiper belt, a halo of icy bodies so far from Earth it takes more than six hours for signals to travel at the speed of light to reach the Earth.

But just after 10:30 Eastern time Tuesday, at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, mission operations manager Alice Bowman turned to her colleagues with a wide grin.

The probe's systems were working. Its cameras and recorder were pointed in the right direction.

“We have a healthy spacecraft,” Bowman announced. “We have just completed the most distant fly-by. We are ready for Ultima Thule science transmission – science to help us understand the origins of our solar system.”

At mission control, and in an APL auditorium where the rest of the science team was watching, people jumped from their seats and burst into cheers. The borders of the known world had expanded just a little bit more.

Though coincidental, the timing of New Horizons' encounter – in the early hours of a new year – is “auspicious,” Stern said. At a moment when humanity marks the passage of time, looking forward and thinking back, New Horizons is doing the same.

At 4 billion miles from Earth, Ultima Thule is the farthest celestial body scientists have ever viewed up close; it is a door to future exploration in a region that is still almost entirely unknown. But it is also a window to the past – a time capsule from the era when the planets formed, which might contain clues about how the Earth came to be.

Already, scientists are analyzing early data collected just before the moment of closest approach. An image taken from half a million miles away from Ultima Thule showed a blurry bowling pin-shaped body about 20 miles across.

Until New Horizons' fly-by, no person had ever seen a Kuiper belt object as anything but a pinpoint of light in the distance. By today, the scientists at APL will receive their first high-resolution images of the distant rock, revealing whether it has craters, and whether it is one long object or comprises two small bodies orbiting each other.

As for answers to other questions about the Kuiper belt object, Stern advised patience. “This mission has always been about delayed gratification,” he said. “It took us 12 years to sell the spacecraft, five years to build it, 13 years to get here.”

It will take as long as 20 months for scientists to download and process all the data collected during that brief encounter.

But the resulting science will be worth the wait, project scientist Hal Weaver said. “Ultima Thule will be turned into a real world.”

New Horizons was the first mission dedicated to exploring the outermost edges of the solar system. In 2015, it took the first close-up photos of Pluto, revealing a complex and colorful world mottled with methane mountains and a vast, heart-shaped nitrogen ice plain.

Tuesday's encounter was riddled with uncertainties, making it among the more difficult feats NASA has attempted. Ultima Thule is 1 percent the size of Pluto, and New Horizons had to get four times closer to image it. At the moment of closest approach, the spacecraft was moving at 32,000 mph. If its cameras were slightly off track, or if scientists' projections about Ultima Thule's trajectory were just a bit wrong, the probe might fail to capture useful information about its target.

Besides, New Horizons is a 13-year-old vehicle; operators must carefully prioritize their use of remaining fuel.

“This is history-making, what we're doing, in more ways than one,” Stern said.